Just for fun, this works as long as the script is only running under a parent shell :-)

my $psres = `ps -xf`;
my @psres=split /\n/,$psres;
for (my $i = 0; $i < @psres; ++$i){
    if ($psres[$i] =~ /bash/ && $psres[++$i] =~ /\s+\\_\sperl\sscriptn
+ame\.pl/){
            print "$1\n" if $psres[--$i] =~ /\s(\d+[^\s])/;
    }
}
[download]

Obviously though, there are much better solutions to what you actually wanted above..